36 DROSERA ROTUNDIFOLIA. CHAP. II. 



though the secretion is so viscid that it can be re- 

 moved with difficulty merely by waving the leaves in 

 water. If the falling drops of water are small, they 

 adhere to the secretion, the weight of which must be 

 increased in a much greater degree, as before re- 

 marked, than by the addition of minute particles of 

 solid matter ; yet the drops never cause the tentacles 

 to become inflected. It would obviously have been a 

 great evil to the plant (as in the case of occasional 

 touches) if the tentacles were excited to bend by 

 every shower of rain ; but this evil has been avoided 

 by the glands either having become through habit 

 insensible to the blows and prolonged pressure of 

 drops of water, or to their having been originally 

 rendered sensitive solely to the contact of solid bodies. 

 We shall hereafter see that the filaments on the leaves 

 of Dionsea are likewise insensible to the impact of 

 fluids, though exquisitely sensitive to momentary 

 touches from any solid body. 



When the pedicel of a tentacle is cut off by a 

 sharp pair of scissors quite close beneath the gland, 

 the tentacle generally becomes inflected. I tried this 

 experiment repeatedly, as I was much surprised at the 

 fact, for all other parts of the pedicels are insensible to 

 any stimulus. These headless tentacles after a time 

 re-expand ; but I shall return to this subject. On the 

 other hand, I occasionally succeeded in crushing a 

 gland between a pair of pincers, but this caused no 

 inflection. In this latter case the tentacles seem 

 paralysed, as likewise follows from the action of tou 

 strong solutions of certain salts, and by too great 

 heat, whilst weaker solutions of the same salts and a 

 more gentle heat cause movement. We shall also see 

 in future chapters that various other fluids, some 



